1. Field
The present invention relates generally to steering mechanisms which respond to weight changes made by the operator and more specifically to a steering truck for use with skateboards, roller skates, scooters, and other similar skate-type devices wherein the wheels are not only turned but also tilted responsive to an operator's weight changes.
2. Prior Art
Steering trucks and similar steering mechanisms which are weight responsive are well known in the art. Generally, such mechanisms are attached to the bottom face of a platform or similar planar member upon which a weight rests or stands. Responsive to a change in the center of mass of the weight from one longitudinal side to the other, the platform tilts slightly to cause the mechanism to adjust the direction in which attached wheels are pointing.
While necessarily small in diameter, the wheels attached to such mechanisms have a relatively substantial width, such width often exceeding that of the diameter. Typical of this type of steering mechanism are U.S. Pat. No. 2,509,324, issued to Van Horn in 1986 and U.S. Pat. No. 4,398,734, issued to Barnard in 1983. Both the Barnard and Van Horn patents disclose a plunger which is rigidly affixed at one end to the bottom face of a platform, the plunger extending downwardly. An axle having wheels rotatably attached at both ends is affixed to the other end of the plunger, the axle including a leg which extends forwardly. The leg is attached to a leg holder which allows universal movement of the leg.
In this manner, when the center of mass of a weight atop the platform is shifted to one side of the platform or another, the platform and plunger correspondingly shift or tilt slightly, the plunger thereby causing the axle and wheels to turn.
While adequate for a number of applications, the type of steering truck just described includes a number of disadvantages. For example, this configuration requires that the wheels be fairly close together. This can become a problem when the steering mechanism is called upon to make sharp turns since the platform may tilt far enough over to make contact with the wheels. Thus, this configuration not only limits the turning radius of this type of steering mechanism, but the platform contacting the wheels can cause a dangerous situation as well.
For example, many skateboard riders, when riding their skateboard, have parts of their feet which hang over the edge of the platform. When making a sharp turn, it is not only conceivable, but probable, that this portion of the rider's foot which is hanging over the edge of the platform will come in contact with a wheel, or wheels, thereby throwing the rider off balance and probably causing an accident. Also, if the platform can come in contact with the wheels during a turn, undue wear and tear is caused on both the wheels and the platform.
Another problem caused by the configuration mentioned above is the size of the wheels. While providing a greater contact area with the ground, such wheels cannot tilt into a turn to assist in gripping the ground surface. Indeed, even assuming that such steering mechanisms provided for tilt in the wheels, which they do not, the extra wide wheels commonly used on skateboards could not be tilted during a turning manoeuver without virtually eliminating the ground contact sought to the maintained by use of the wide wheels. Thus, without the ability to tilt, horizontal forces experienced during the course of a turn, caused by the tendency of an object to travel in a straight path, must be completely absorbed by frictional forces between the wheels and the ground.
Therefore, there exists in the prior art a legitimate need for a steering mechanism which not only provides steering capabilities, but also provides tilting capabilities as well to allow increased turning capacity.